Members of the genus Chlamydia are obligately intracellular parasitic bacteria which cause various diseases of animals and man. The purpose of this proposal is to investigate the mechanisms by which Chlamydiae attach to and grow within host cells. Studies will include investigation of the function and antigenicity of an outer membrane protein of Chlamydia psittaci. The mechanisms by which host-free Chlamydiae transport nucleotides and concentrate amino acids will be investigated. Attempts will be made to detect and to maximize host-free synthesis of RNA, DNA, and protein. A long range goal of this research is to establish conditions for host-free growth of clamydiae.